Piles used for fixing soil holding means, for example, a soil holding fence, can be classified into ground-standing piles and suspension piles. A ground-standing pile includes a pile body which is used as a fixing means for a soil holding means and a pile foot which is driven into soil. A suspension pile includes only a pile body which is suspended onto slopes and is linked to other suspension piles by using interlocking bars when are to be used. The interlocking bars can also provide the interlocks between each suspension piles disposed in different sections of a step-shaped slope so as to improve the total strength of the suspension piles.
Soil dressing vegetation is an important technique in the soil conservation technique. When the natural environment is not suitable for the growth of plants, soil dressing is provided on slopes to improve the natural environment. However, the soil dressing that is provided on a slope is easily washed away when it rains. Whether the soil dressing is easily washed away depends on whether the soil holding means can be firmly fixed on the slope or not.
Among conventional soil holding means, except for some concrete made holding means which are fixed on slopes by using a specific fixing method, other soil holding means are fixed on slopes by using a plurality of independent piles, ground-standing piles or suspension piles which are driven into the slope or firmly secured on the slope by interlocking bars respectively.
Conventional soil holding means are described in more detail as follows.
Referring to FIG. 1, there is shown a contour-type soil holding fence used for holding soil dressing., in which soil holding fences 1002 which are mounted with water permeable nets 1001 are supported by a plurality of independent ground-standing piles 1003 and are disposed on slope 1004 having an original inclined plane 1000. Note that soil dressing is usually paved on the original inclined plane 1000 to a thickness that is in alignment with the soil dressing inclined plane as indicated by broken line 1000-1. As the component gravity force of the soil dressing along the direction of the soil dressing inclined plane 1000-1 will be exerted on each independent ground-standing piles 1003 via soil holding fences 1002, if independent piles are driven into the slope 1004 to a sufficient depth and the soil paved on the original inclined plane 1000 is hard enough, independent ground-standing piles 1003 can remain uninclined and the soil dressing can be held between two soil holding fences 1002. However, in the case ground-standing independent piles 1003 are not driven into the slope 1004 to a sufficient depth and/or the soil dressing held between two soil holding fences 1002 is not hard enough, each of the independent ground-standing piles 1003 has a tendency to incline and thus the soil dressing paved on the slope 1004 are easily washed away when it rains.
Referring to FIG. 2, there is shown another conventional soil holding means which consists of a plurality of interlinked square soil holding net units in which at the corner of each square net unit, which is located at the upper portion of each square net unit, is driven into an independent ground-standing pile 2003 respectively. As the component gravity force of the soil dressing along the slope is also exerted on each independent ground-standing pile 2003, the same problem arises.
Referring to FIG. 3, there is shown a further conventional soil holding means which is a honeycomb-type soil holding means. A plurality of hexangular net units 3001 are supported by independent ground-standing piles 3003 which can be provided at the inside of any corners of each hexangular net unit 3001. Although the washing away of soil dressing can be effectively prevented by this means, this holding means necessitates a large number of independent ground-standing piles 3003 and thus the cost of constructing this means is high.
Aside from the above problems, when the slope to be paved with soil dressing is steep, hard, full of deep ditches and large, it is more difficult to set up the above conventional soil holding means, and thus usually after the setting up of the soil holding means, it is necessary to do some reinforcing and adjusting operations.